Cooling System for High Density Heat Loads

ABSTRACT

A pumped refrigerant cooling system having multiple pumping units for providing working fluid to a load to enable cooling of a space via the load. The pumped refrigerant cooling system operates the pumping units at less than capacity. When a pumping unit is deactivated, the output of the remaining pumping units is increased to maintain fluid flow.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Divisional application Ser. No.15/498,586, filed on Apr. 27, 2017, which is a divisional of U.S.application Ser. No. 13/723,661, filed on Dec. 21, 2012, which claimsthe benefit of U.S. Provisional Application No. 61/580,686 filed on Dec.28, 2011. The entire disclosures of each of the above applications areincorporated herein by reference.

FIELD

The present disclosure relates to pumped refrigerant cooling systems forprecision cooling applications having 1+1 to N+1 primary cooling circuitredundancy.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A data center is a room containing a collection of electronic equipment,such as computer servers. Data centers and the equipment containedtherein typically have optimal environmental operating conditions,temperature and humidity in particular. A climate control systemmaintains the proper temperature and humidity in the data center.

The climate control system includes a cooling system that cools air andprovides the cooled air to the data center. The cooling system mayinclude air conditioning units, such as computer room air conditioningunit (CRAC) or computer room air handlers (CRAH) that cools the air thatis provided to the data center. The data center may have a raised floorand the cooled air introduced into the data center through vents in theraised floor. The raised floor may be constructed to provide a plenumbetween the cold air outlet of the CRAC (or CRACs) or CRAH (or CRAHS)and the vents in the raised floor, or a separate plenum such as a ductmay be used.

The data center could also have a hard floor. The CRACS may, forexample, be arranged in the rows of the electronic equipment, may bedisposed with their cool air supply facing respective cold aisles, or bedisposed along walls of the data center. The equipment racks in the datacenter may be arranged in a hot aisle/cold aisle configuration with theequipment racks arranged in rows. The cold air inlets of the racks,typically at the front of the racks, in one row face the cold air inletsof the racks in a row across a cold aisle, and the hot air outlets ofthe racks in one row face the hot air outlets of the racks in a rowacross a hot aisle.

One type of cooling system uses a pumped refrigerant cooling unit, suchas the cooling units used in the XD System available from LiebertCorporation of Columbus, Ohio. The Liebert XD System has two coolingloops, that may also be referred to as cooling circuits or cycles. Aprimary loop uses chilled water or a refrigerant, such as R407C and asecondary loop uses a pumped refrigerant, such as R134a. The primaryloop includes a fluid to fluid heat exchanger to cool the pumpedrefrigerant circulating in the secondary loop. The secondary loopincludes one or more phase change cooling modules having a fluid to airheat exchanger through which the pumped refrigerant is circulated tocool air flowing across the heat exchanger.

Basic schematics for the two cooling loops (or cycles) of the Liebert XDSystem are shown and described in U.S. Ser. No. 10/904,889 for “CoolingSystem for High Density Heat Load,” the entire disclosure of which isincorporated herein by reference. FIGS. 1 and 2 of this application areincluded herein as FIGS. 1 and 2 along with the accompanying descriptionfrom this application.

Referring to FIGS. 1 and 2, the disclosed cooling system 10 includes afirst cooling cycle 12 (the primary cooling loop) in thermalcommunication with a second cycle 14 (the secondary cooling loop). Thedisclosed cooling system 10 also includes a control system 90. Both thefirst and second cycles 12 and 14 include independent working fluids.The working fluid in the second cycle is any volatile fluid suitable foruse as a conventional refrigerant, including but not limited tochlorofluorocarbons (CFCs), hydro fluorocarbons (HFCs), orhydrochloro-fluorocarbons (HCFCs). Use of a volatile working fluideliminates using water located near sensitive equipment, as is sometimesdone in conventional systems for cooling computer rooms. The secondcycle 14 includes a pump 20, one or more first heat exchangers(evaporators) 30, a second heat exchanger 40, and piping to interconnectthe various components of the second cycle 14. The second cycle 14 isnot a vapor compression refrigeration system. Instead, the second cycle14 uses the pump 20 instead of a compressor to circulate a volatileworking fluid for removing heat from a heat load. The pump 20 ispreferably capable of pumping the volatile working fluid throughout thesecond cooling cycle 14 and is preferably controlled by the controlsystem implemented by controller 90.

The first heat exchanger 30 is an air-to-fluid heat exchanger thatremoves heat from the heat load (not shown) to the second working fluidas the second working fluid passes through the second fluid path infirst heat exchanger 30. For example, the air-to-fluid heat exchanger 30can include a plurality of tubes for the working fluid arranged to allowwarm air to pass therebetween. It will be appreciated that a number ofair-to-fluid heat exchangers known in the art can be used with thedisclosed cooling system 10. A flow regulator 32 can be connectedbetween the piping 22 and the inlet of the evaporator 30 to regulate theflow of working fluid into the evaporator 30. The flow regulator 32 canbe a solenoid valve or other type of device for regulating flow in thecooling system 10. The flow regulator 32 preferably maintains a constantoutput flow independent of the inlet pressure over the operatingpressure range of the system. In the embodiment of FIGS. 1 and 2, thesecond cycle 14 includes a plurality of evaporators 30 and flowregulators 32 connected to the piping 22. However, the disclosed systemcan have one or more than one evaporator 30 and flow regulators 32connected to the piping 22.

The second heat exchanger 40 is a fluid-to-fluid heat exchanger thattransfers heat from the second working fluid to the first cycle 12. Itwill be appreciated that a number of fluid-to-fluid heat exchangersknown in the art can be used with the disclosed cooling system 10. Forexample, the fluid-to-fluid heat exchanger 40 can include a plurality oftubes for one fluid positioned in a chamber or shell containing a secondfluid. A coaxial (“tube-in-tube”) exchanger would also be suitable. Incertain embodiments, it is preferred to use a plate heat exchanger. Thesecond cycle 14 can also include a receiver 50 connected to the outletpiping 46 of the second heat exchanger 40 by a receiver output line 52.The receiver 50 may store and accumulate the working fluid in the secondcycle 14 to allow for changes in the temperature and heat load.

In one embodiment, the air-to-fluid heat exchanger 30 can be used tocool a room holding computer equipment. For example, a fan 34 can drawair from the room (heat load) through the heat exchanger 30 where thesecond working fluid absorbs heat from the air. In another embodiment,the air-to-fluid heat exchanger 30 can be used to directly remove heatfrom electronic equipment (heat load) that generates the heat bymounting the heat exchanger 30 on or close to the equipment. Forexample, electronic equipment is typically contained in an enclosure(not shown). The heat exchanger 30 can mount to the enclosure, and fans34 can draw air from the enclosure through the heat exchanger 30. Thefirst heat exchanger 30 could be an alternate type of heat exchanger(e.g., a cold plate), and may be in direct thermal contact with the heatsource. It will be appreciated by those skilled in the art that the heattransfer rates, sizes, and other design variables of the components ofthe disclosed cooling system 10 depend on the size of the disclosedcooling system 10, the magnitude of the heat load to be managed, and onother details of the particular implementation.

In the embodiment of the disclosed cooling system 10 depicted in FIG. 1,the first cycle 12 includes a chilled water cycle 60 connected to thefluid-to-fluid heat exchanger 40 of the second cycle 14. In particular,the second heat exchanger 40 has first and second portions or fluidpaths 42 and 44 in thermal communication with one another. The secondfluid path 42 for the volatile working fluid is connected between thefirst heat exchanger 30 and the pump 20. The first fluid path 44 isconnected to the chilled water cycle 60. The chilled water cycle 60 maybe similar to those known in the art. The chilled water system 60includes a first working fluid that absorbs heat from the second workingfluid passing through the fluid-to-fluid heat exchanger 40. The firstworking fluid is then chilled by techniques known in the art for aconventional chilled water cycle. In general, the first working fluidcan be either volatile or non-volatile. For example, in the embodimentof FIG. 1, the first working fluid can be water, glycol, or mixturesthereof. Therefore, the embodiment of the second cycle 14 in FIG. 1 canbe constructed to include the pump 20, air-to-fluid heat exchanger 30,and fluid-to-fluid heat exchanger 40 and can be connected to an existingchilled water service that is available in the building housing theequipment to be cooled, for example.

In the embodiment of the disclosed cooling system 10 in FIG. 2, thesecond cycle 14 is substantially the same as that described above.However, the first cycle 12 includes a vapor compression refrigerationsystem 70 connected to the first portion or fluid path 44 of heatexchanger 40 of the second cycle 14. Instead of using chilled water toremove the heat from the second cycle 14 as in the embodiment of FIG. 1,the refrigeration system 70 in FIG. 2 is directly connected to or is the“other half” of the fluid-to-fluid heat exchanger 40. The vaporcompression refrigeration system 70 can be substantially similar tothose known in the art. An exemplary vapor compression refrigerationsystem 70 includes a compressor 74, a condenser 76, and an expansiondevice 78. Piping 72 connects these components to one another and to thefirst fluid path 44 of the heat exchanger 40.

The vapor compression refrigeration system 70 removes heat from thesecond working fluid passing through the second heat exchanger 40 byabsorbing heat from the exchanger 40 with a first working fluid andexpelling that heat to the environment (not shown). For example, in theembodiment of FIG. 2, the first working fluid can be any conventionalchemical refrigerant, including but not limited to chlorofluorocarbons(CFCs), hydrofluorocarbons (HFCs), or hydrochloro-fluorocarbons (HCFCs).The expansion device 78 can be a valve, orifice or other apparatus knownto those skilled in the art to produce a pressure drop in the workingfluid passing therethrough. The compressor 74 can be any type ofcompressor known in the art to be suitable for refrigerant service suchas reciprocating compressors, scroll compressors, or the like. In theembodiment depicted in FIG. 2, the cooling system 10 is self-contained.For example, the vapor compression refrigeration system 70 can be partof a single unit that also houses pump 20 and fluid-to-fluid heatexchanger 30.

During operation of the disclosed system, pump 20 moves the workingfluid via piping 22 to the air-to-fluid heat exchanger 30. Pumpingincreases the pressure of the working fluid, while its enthalpy remainssubstantially the same. The pumped working fluid then enters theair-to-fluid heat exchanger or evaporator 30 of the second cycle 14after passing through flow regulator 32. A fan 34 can draw air from theheat load through the heat exchanger 30. As the warm air from the heatload (not shown) enters the air-to-fluid heat exchanger 30, the volatileworking fluid absorbs the heat. As the fluid warms through the heatexchanger, some of the volatile working fluid will evaporate. In a fullyloaded cooling system 10, the fluid leaving the first heat exchanger 30will be substantially vapor. The vapor flows from the heat exchanger 30through the piping 36 to the fluid-to-fluid heat exchanger 40. In thereturn line or piping 36, the working fluid is substantially vapor, andthe pressure of the fluid drops while its enthalpy remains substantiallyconstant. At the fluid-to-fluid heat exchanger 40, the vapor in thesecond fluid path 42 is condensed by transferring heat to the first,colder fluid of the first cycle 12 in the first fluid path 44. Thecondensed working fluid leaves the heat exchanger 40 via piping 46 andenters the pump 20, where the second cycle 14 can be repeated.

The first cooling cycle 12 operates in conjunction with second cycle 14to remove heat from the second cycle 14 by absorbing the heat from thesecond working fluid into the first working fluid and rejecting the heatto the environment (not shown). As noted above, the first cycle 12 caninclude a chilled water system 60 as shown in FIG. 1 or a vaporcompression refrigeration system 70 as shown in FIG. 2. During operationof chilled water system 60 in FIG. 1, for example, a first working fluidcan flow through the first fluid path 44 of heat exchanger 40 and can becooled in a cooling tower (not shown). During operation of refrigerationsystem 70 in FIG. 2, for example, the first working fluid passes throughthe first portion 44 of fluid-to-fluid heat exchanger 40 and absorbsheat from the volatile fluid in the second cycle 14. The working fluidevaporates in the process. The vapor travels to the compressor 74 wherethe working fluid is compressed. The compressor 74 can be areciprocating, scroll or other type of compressor known in the art.After compression, the working fluid travels through a discharge line tothe condenser 76, where heat from the working fluid is dissipated to anexternal heat sink, e.g., the outdoor environment. Upon leavingcondenser 76, refrigerant flows through a liquid line to expansiondevice 78. As the refrigerant passes through the expansion device 78,the first working fluid experiences a pressure drop. Upon leavingexpansion device 78, the working fluid flows through the first fluidpath of fluid-to-fluid heat exchanger 40, which acts as an evaporatorfor the refrigeration system 70.

Data center providers are continually seeking increased reliability andup time from climate control systems. Therefore, data center providerscontinually desire improved redundancy in the climate control systems toguard against unnecessary down time of the cooled electronic equipmentdue to unexpected interruption in operation of the climate controlsystems. One mode of redundancy is to replicate each element of acooling system, such as the first cooling cycle 12 and the secondcooling cycle 14. Such complete redundancy can be prohibitivelyexpensive and greatly complicates the design, implementation, andcontrol of the cooling systems. In various configurations, redundancymay include implementation of a cooling loop, including a second,reduced implementation of a second cooling cycle 14 such as shown inFIGS. 1 and 2. The reduced redundancy could include a second pump unit20 and half of the heat exchangers provided in the primary coolingsystem. Implementing this redundant system would also require theassociated plumbing and controls. Accordingly, an approximate cost ofsuch a system could be in the range of 50% of the total cost of the basecooling load.

Another approach to redundancy in order to minimize equipment caninclude over-provisioning the environment by deploying cooling modulesin complicated, interweaved schemes. Failure of one cooling loop canthen be covered by other cooling loops interwoven into the zone of thefailed one cooling loop. Such over provisioning again provides increasedcost to the consumer which includes extra pumps, cooling modules,plumbing, piping and control systems over conventional configurationsshown in FIGS. 1 and 2.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

A cooling system having a plurality of pumping units to supply coolingfluid to a load. In various configurations, the pumping units supply aportion of the cooling fluid to the load. If a pumping unit experiencesa fault condition, the output of the other pumping unit is increased tomaintain sufficient fluid flow to the load. In other configurations, anadditional pumping unit is provided which does not normally supply fluidflow to the load. When one of the other pumping units experiences afault condition, the additional pumping unit is activated to providefluid flow to the load. In other configurations, a plurality of pumpingunits provides fluid flow to a plurality of respective loads. When oneof the pumping units experiences a fault condition, a redundant pumpingunit is inserted into the circuit to supply fluid flow to the loadassociated with the fault condition pumping unit.

A cooling system includes a first cooling module, the cooling modulehaving a first variable speed pump circulating refrigerant through aload. The cooling system also has a second cooling module, the secondcooling module having a second variable speed pump circulatingrefrigerant through the load. The first and second variable speed pumpsoperate at less than full speed. When one of the first cooling module orthe second cooling modules cannot sufficiently circulate refrigerantthrough the load, the speed of the variable speed pump of another of thefirst or second cooling modules is increased to compensate for the onecooling module.

A cooling system includes a plurality of cooling modules supplyingrefrigerant to a load, a plurality of cooling modules each has avariable speed pump for supplying the refrigerant to the load. Thevariable speed pumps operate at less than full speed. When one of theplurality of cooling modules cannot sufficiently supply refrigerant, aspeed of the variable speed pump of at least one of another of theplurality of cooling modules having a variable speed that is increasedto compensate for the one of the plurality of cooling modules.

A method for providing redundant cooling in a cooling system includesproviding a plurality of cooling modules. The plurality of coolingmodules cooperate to pump cooling fluid to at least one thermal load.The cooling modules operating at variable speeds. The speed of one ofthe plurality of cooling modules is increased when another of theplurality of cooling modules experiences a decrease in speed. The speedof the one of the plurality of cooling modules is decreased when anotherof the plurality of cooling modules experiences an increase in speed.

A method for providing redundant cooling module in a cooling systemincludes providing a first cooling module. The first cooling moduleprovides cooling fluid to a thermal load. The first cooling moduleoperates at variable speeds. The first cooling module has a first normaloperating speed, the first normal operating speed being less than a fullspeed. Providing a second cooling module. The second cooling moduleprovides cooling fluid to the thermal load. The second cooling moduleoperates at variable speeds, the second cooling module having a secondnormal operating speed, the second normal operating speed being lessthan a full speed. Increasing the speed of one of the first coolingmodule or second cooling module when the other of the first coolingmodule or second cooling module is operating at a speed less than itsrespective normal operating speed. Decreasing the speed of the firstcooling module or second cooling module when the other of the firstcooling module or second cooling module experiences an increase inspeed.

A cooling system including: a primary cooling module. The primarycooling module supplying refrigerant to a load. A secondary coolingmodule provides a supplemental flow of refrigerant to the load upondetection of a deficiency of the primary cooling module.

A cooling system including: a plurality of primary cooling modules. Theprimary cooling modules supply refrigerant to a respective one of aplurality of thermal loads. A secondary cooling module selectivelyprovides a supplemental flow of refrigerant through the load associatedwith a primary cooling module for which a fault has been detected.

A method for providing redundant cooling in a cooling system includesproviding a primary cooling module having a circuit. The primary coolingmodule provides cooling fluid to a thermal load. Providing a secondarycooling module, and initiating operation of the secondary cooling moduleupon detection of a fault in the primary cooling module. Inserting thesecondary cooling module into the circuit, the secondary cooling moduleproviding cooling fluid to the thermal load, and deactivating theprimary cooling module.

A method for providing redundant control of a cooling system includesproviding a plurality of primary cooling modules. The primary coolingmodules circulates refrigerant through a respective thermal load.Providing a secondary cooling module. The secondary cooling moduleselectively provides a supplemental flow of refrigerant through the loadassociated with a selected primary cooling module when a fault isdetected in one of the primary cooling modules.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic view of a primary cooling loop connected to achilled water cycle;

FIG. 2 is a schematic view of a cooling system having a primary coolingloop utilizing a vapor compression refrigeration system;

FIG. 3 is a schematic view of a cooling system arranged according tovarious embodiments;

FIG. 4 is a schematic view of a cooling system arranged according tovarious embodiments;

FIG. 5 is a flow diagram depicting a process for providing redundantcooling capacity in a system having a redundant cooling source, such asFIGS. 3 and 4;

FIG. 6. is a schematic view of a cooling system arranged according toanother various embodiment;

FIG. 7 is a flow diagram depicting a process for providing redundantcooling in the system of FIG. 6;

FIG. 8 is a schematic view of a cooling system arranged according toanother various embodiment; and

FIG. 9 is a flow diagram depicting a process for providing redundantcooling in the system of FIG. 9.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

FIG. 3 depicts a schematic view of a pumped refrigerant cooling system100 arranged in accordance with various embodiments. The pumpedrefrigerant cooling system 100 includes a pair of pumping units 120 a,120 b. Pumping units 120 a, 120 b provide a working fluid pumped to aload 122. Load 122 is placed in an environment to cool, such as a dataroom. In some instances, n elements may be described collectively usingthe reference numeral without the a, b, . . . , n. Further, likereference numerals will be used to describe similar elements throughoutthe specification. In various configurations, load 122 can include aplurality of loads 122, referred to collectively as load 122.

Each pumping unit 120 includes a first pump 124 and a second pump 126which pump the working fluid at an elevated pressure to respective checkvalves 132, 134. Pumps 124, 126 can be arranged in a first, redundantconfiguration. Alternatively, pumps 124, 126 can be arranged tocooperatively apply fluid at an output pressure and fluid flow throughrespective check valves 132, 134 to output line 136. Pumps 124, 126 canbe controlled to provide both redundant and cooperative operation.

Fluid pumped through output line 136 is applied to load 122. Load 122may assume a number of configurations, including a configuration similarto evaporator 30 of FIGS. 1 and 2. Load 122 is placed in an environmentwhere it is desirable to remove heat from the environment in which load122 is situated by transferring the heat to fluid pumped through outputline 136. Fluid from output line 136 enters load 122 at a firsttemperature and exits load 122 on line 140 at an elevated temperature.Fluid pumped through load 122 may also change phase from a liquid phaseto a gaseous phase. Line 140, generally referred to as inlet line 140,returns the working fluid to pumping unit 120.

Fluid in inlet line 140 is input to condenser 138. Condenser 138receives the working fluid at a first, elevated temperature and rejectsthe heat in the working fluid to output fluid at a reduced temperature.Fluid passing through condenser 138 changes phase from a gaseous to aliquid phase. The fluid output at a reduced temperature is outputthrough return line 144 which is input to receiver 142. Receiver 142stores working fluid for use by pumping unit 120. Receiver 142 returnsworking fluid to respective pumps 124, 126 via receiver output line 143.A bypass line 145 bypasses receiver enabling fluid to pass from theoutlet of condenser 138 directly to receiver output line 143, bypassingreceiver 142. Receiver output line 143 provides working fluid to pumps124, 126 via respective pump input lines 148, 150. A controller 146connects to each pumping unit 120, and sends and receives sense andcontrol signals to and from each main pumping unit 120.

In operation, respective pumping units 120 a, 120 b each provideapproximately 50% of the required refrigerant flow to load 122. When ascenario occurs that either of pumping units 120 a or 120 b providesless than the predetermined capacity, such as 50%, the other pumpingunit 120 a, 120 b can be controlled by controller 146 to increase theoutput. The output may be increased by increasing the output of theother pump unit 120 a, 120 b to maintain sufficient fluid flow to load122. When it is determined that the pumping unit previously determinedto be providing less than full capacity is fully back online, the outputof each pumping unit 120 a, 120 b can be returned to a predeterminedoperation, such as 50% of full load.

FIG. 4 depicts a schematic view of a pumped refrigerant cooling system200 arranged in accordance with various embodiments. FIG. 4 is arrangedsimilarly to FIG. 3 described above, but includes more than two pumpingunits 120. The pumped refrigerant cooling system 200 includes aplurality of primary pumping units 120 a, 120 b, . . . , 120 n. Eachpumping unit 120 a, 120 b, . . . , 120 n provides a working fluid pumpedto load 122 or a plurality of loads 122 arranged in parallel. Load 122is placed in an environment to be cooled, such as a data room. It shouldbe noted that n can be any positive integer and represents a selectednumber of similarly arranged elements in the figures. For example,pumping units 120 a, 120 b, . . . , 120 n refer to N pumping units. Thenumber of pumping units can be varied depending on the particularimplementation of the pumped refrigerant cooling system 200 describedherein. This numbering convention will be used to describe other similarunits. In some instances, the n pumping units may be describedcollectively using the reference numeral without the a, b, . . . , n.

Operation of the pumped refrigerant cooling systems 100, 200 of FIGS. 3and 4 will be described. Pumped refrigerant cooling system 200 of FIG. 4operates similarly to the pumped refrigerant cooling system 100 of FIG.3. Particularly, pumped refrigerant cooling system 200 operatessimilarly except that it has multiple pumping units 120 rather than thepair of pumping units 120 described in connection with FIG. 3.

In operation, pumping units 120 operate at less than full capacity toshare a portion of the fluid flow provided to load 122. In variousconfigurations the distribution may be equal. In other configurations,the distribution need not be equal. When any of the N pumping units isdisabled by controller 146, a controller 146 also increases the outputof the remaining (N−1) pumping units 120 to load 122 to maintainsufficient refrigerant flow through load 122. By way of non-limitingexample, if N=3, and the refrigerant flow is divided equally among thethree pumping units 120, each pumping unit applies 33.33% of the overallrefrigerant flow to load 122. If any one of the N units should bedeactivated by controller 146, the remaining (N−1) units provide theremaining refrigerant flow to load 122. In this instance, each of theremaining (N−1) units will provide approximately 50% of the totalrefrigerant flow to load 122. In another non-limiting example, if N=5,each of the primary pumping units 120 may provide 20% of the totalrefrigerant flow to load 122. If controller 146 deactivates one of thepumping units 120, the remaining four pumping units provide 25% of theoverall refrigerant flow. While the examples described herein aredirected to each pumping unit 120 providing equal refrigerant flow, oneskilled in the art would recognize that the pumping units 120 couldprovide unequal flow so long as the pumping units 120 remaining onlinecan provide sufficient refrigerant flow to load 122.

FIG. 5 depicts a block diagram for providing redundancy of the pumpingunits in the pumped refrigerant cooling system of FIGS. 3 and 4. Theprocess begins at start block 151 and proceeds to decision block 152.Decision block 152 determines if a fault has been detected in one of thepumping units 120. If no fault has been detected, control proceeds backto the beginning of decision block 152 which continues to monitorwhether a fault condition has been detected in a pumping unit. If afault condition has been detected in a pumping unit, control proceeds toblock 154 where controller 146 provides a signal to increase the speedof the (N−1) pumping units other than the fault condition pumping unit.Once the output of the remaining (N−1) pumping units 120 has beensufficiently increased, control proceeds to block 156. At block 156,controller 146 adjusts the output of pumping unit 120 fault conditionpumping unit 120. Controller 146 can either decrease the requestedoutput of the fault condition pumping unit 120 or deactivate the faultcondition pumping unit 120. Control then proceeds to block 158 whichmonitors for an indication that the fault condition pumping unit 120 hasreturned to normal operation. If the fault condition pumping unit hasnot returned to normal operation, control proceeds back to the beginningof decision block 158. When the fault condition pumping unit isdetermined to be operating properly, control proceeds to block 160. Atblock 160, controller 146 generates control signals to restore faultcondition pumping unit 120 previously to its normal operation output.Control then proceeds to block 162. At block 162, controller 146decreases the speed of the (N−1) pumping units 120 whose speed waspreviously increased in order to compensate for the prior deactivationor reduction of output of the fault condition pumping unit 120. Controlthen proceeds to block 164 where the process is completed.

FIG. 6. depicts a cooling system 300 arranged in accordance with variousembodiments. The cooling system 300 includes pumping units 120 a, 120 b,. . . , 120 n which are arranged similarly to pumping units 120described previously herein. Pumping units 120 provide fluid flow to apair of cooling modules or loads 122 a, 122 b shown arranged inparallel. The configuration of FIG. 6 is directed to a system includinga pumping unit operating as a standby pumping unit that is activatedwhen one or more of the other (N−1) pumping units must be deactivated.The standby pumping unit 120 then becomes activated and inserted intothe circuit while the other pumping unit is deactivated by thecontroller 146.

FIG. 6 is arranged similarly to the various embodiments described above.FIG. 6 also includes inlet valves 170 a, 170 b, . . . , 170 n associatedwith respective pumping units 120 a, 120 b, . . . , 120 n. FIG. 6 alsoincludes outlet valves 172 a, 172 b, . . . , 172 n associated withrespective pumping units 120 a, 120 b, . . . , 120 n. Inlet valves 170and outlet valves 172 cooperate to enable and disable fluid flow to andfrom respective pumping units 120. Pumping unit 120 n of the N pumpingunits function as a standby pumping unit and is activated to providefluid flow replacing the fluid flow of one or more of the other (N−1)pumping units 120 when deactivated.

FIG. 7 depicts a block diagram of the operation of the pumpedrefrigerant cooling system 300 of FIG. 6. Control begins at start block180 and proceeds to decision block 182. At decision block 182 thecontroller 146, or other portion of the system 300, determines whether afault condition has been detected in a pumping unit 120. If no fault hasbeen detected, control proceeds back to decision block 182. If a faulthas been detected, control proceeds to block 184. At block 184,controller 146 brings the standby pumping unit, 120 n in this example,online so that standby pumping unit 120 n can provide pressurized fluidflow. Control then proceeds to block 186 where controller 146 places thestandby pumping unit 120 n into the circuit by opening inlet valve 170 nand outlet valve 172 n. This enables standby pumping unit 120 n toprovide fluid flow to load 122. Control then proceeds to block 188 wherethe fault condition pumping unit 120 is removed from the circuit.Controller 146 removes the fault condition pumping unit 120 by closingits corresponding inlet valve 170 and outlet valve 172 in order to takethe faulty pumping unit out of the circuit. Control next proceeds todecision block 190. At decision block 190, controller 146 determineswhether the fault condition pumping unit is determined to be operatingproperly. If the deactivated pumping unit is not operating properly,control returns to decision block 190. If the fault condition pumpingunit is determined to be operating properly. Control proceeds to block192, and controller 146 brings the now properly operating pumping unit120 back online so that it can provide fluid flow of cooling fluid tothe loads 122. Once the fault condition pumping unit is brought online,control proceeds to block 194. At block 194, the fault condition pumpingunit is placed into the circuit by opening its respective inlet valve170 and outlet valve 172 to enable fluid flow to load 122. Control thenproceeds to block 196. At block 196, controller 146 removes the standbypumping unit 120 n from the circuit by closing inlet valve 170 n andoutlet valve 172 n. Control then proceeds to block 198 in whichcontroller 146 deactivates standby pumping units 120. Control thenproceeds to end block 199.

FIG. 8 depicts a schematic view of a pumped refrigerant cooling system400 having a redundant pumping unit. As described above, the pumpedrefrigerant cooling system 400 includes a plurality of main or primarypumping units 120 a, 120 b, . . . , 120 n. Each primary pumping unit 120a, 120 b, . . . , 120 n provides a working fluid pumped to a load 122 a,122 b, . . . , 122 n. Each load 122 a, 122 b, . . . , 122 n is placed inan environment to cool the environment, such as a data room. It shouldbe noted that n can be any positive integer and represents a selectednumber of similarly arranged elements in the figures. For example,pumping units 120 a, 120 b, . . . , 120 n refer to N pumping units. Asalso described above, one skilled in the art would recognize that thenumber of pumping units can be varied depending on the particularimplementation of the pumped refrigerant cooling system 400 describedherein.

Each main pumping unit 120 includes a first pump 124 and a second pump126 which pump the working fluid at an elevated pressure to respectivecheck valves 132, 134. Pumps 124, 126 can be arranged in a first,redundant configuration. Alternatively, pumps 124, 126 can be arrangedto cooperatively apply fluid at an output pressure and fluid flowthrough respective check valves 132, 134 to output line 136. Pumps 124,126 can be controlled to provide both redundant and cooperativeoperation.

Fluid pumped through output line 136 is applied to load 122. Load 122may assume a number of configurations, including a configuration similarto evaporator 30 of FIGS. 1 and 2. Load 122 is placed in an environmentwhere it is desirable to remove heat from the environment in which load122 is situated by transferring the heat to fluid pumped through outputline 136. Fluid from output line 136 enters load 122 at a firsttemperature and exits load 122 on line 140 at an elevated temperature.Fluid pumped through load 122 may also change phase from a liquid phaseto a gaseous phase. Line 140, generally referred to as inlet line 140,returns the working fluid to main pumping unit 120.

Fluid in inlet line 140 is input to condenser 138. Condenser 138receives the working fluid at a first, elevated temperature and rejectsthe heat in the working fluid to output fluid at a reduced temperature.Fluid passing through condenser 138 changes phase from a gaseous to aliquid phase. The fluid output at a reduced temperature is outputthrough return line 144 which is input to receiver 142. Receiver 142restores working fluid for use by pumping unit 120. Receiver 142 returnsworking fluid to respective pumps 124, 126 via receiver output line 143.A bypass line 145 bypasses receiver enabling fluid to pass from theoutlet of condenser 138 directly to receiver output line 143, bypassingreceiver 142. Receiver output line 143 provides working fluid to pumps124, 126 via respective pump input lines 148, 150.

In addition to main pumping units 120 a, 120 b, . . . , 120 n, aredundant or standby pumping unit 120′ is included in the pumpedrefrigerant cooling system 400 of FIG. 8. Redundant pumping unit 120′provides working fluid at a pressure in the event that any of mainpumping units 120 a, 120 b, . . . , 120 n should become inactive. Inthis manner, pumping unit 120′ provides redundancy to the other pumpingunits, thereby maintaining up-time and providing a cooling function forany of the loads 122 associated with the deactivated main pumping unit.

Redundant or standby pumping unit 120′ is configured similarly to theabove-described pumping unit 120. Pumping unit 120′ also includes astandby liquid line 136′ and a vapor line 140′. Fluid output from liquidstandby line 136′ can flow to each of loads 122 a, 122 b, . . . , 122 n.Fluid flowing from liquid standby line 136′ flows through one of standbyoutlet valves 208 a, 208 b, . . . , 208 n. Standby liquid lines 210 a,210 b, . . . , 210 n connect to respective standby outlet valves 208 a,208 b, . . . , 208 n and deliver fluid in place of respective pumpingunits 120 a, 120 b, . . . , 120 n. Respective outlet valves 218 a, 218b, . . . , 218 n can be closed to prevent fluid flow in standby liquidlines 210 a, 210 b, . . . , 210 n from flowing into respective pumpingunits 120 a, 120 b, . . . , 120 n. Vapor output from a load 122 a, 122b, . . . , 122 n can be returned to pumping unit 120′ via respectivestandby vapor lines 214 a, 214 b, . . . , 214 n. Standby vapor lines 214a, 214 b, . . . , 214 n connect to respective standby inlet valves 212a, 212 b, . . . , 212 n. Inlet valves 220 a, 220 b, . . . , 220 nassociated with a respective pumping unit 120 a, 120 b, . . . , 120 nprevent vapor from flowing into selected respective pumping units 120 a,120 b, . . . 120 n. Controller 146 sends and receives monitoring andcontrol signals to selected components of pumped refrigerant coolingsystem 400 in order to affect control of pump refrigerant cooling system400.

Operation of the system of FIG. 8 will be described. When a main pumpingunit 120 has become or must be deactivated because various operationalconditions of a main pumping unit 120, redundant pumping unit 120′ isactivated to replace the deactivated main pumping unit. For example, ifmain pumping unit 120 a requires deactivation, redundant pumping unit120′ would be activated to provide the pumping function for deactivatedmain pumping unit 120 a. When this occurs, redundant pumping unit 120′is substituted into the cooling loop from load 122 a to provide fluidflow to load 122 a. This is accomplished through operation of valves 220a, 218 a, 212 a, and 208 a.

For example, in order to insert redundant pumping unit 120′ into theloop to provide fluid to load 122 a, inlet valve 212 a and outlet valve208 a are opened to allow fluid flow to and from pumping unit 120′.Similarly, inlet valve 220 a and outlet valve 218 b are closed in orderto take pumping unit 120 a out of the loop to provide fluid flow to load122 a. Once it is determined to reactivate main pumping unit 120 a,thereby requiring deactivation of redundant pumping unit 120′, a similarprocess to that described above occurs.

FIG. 9 depicts a block diagram of the operation of the pumpedrefrigerant cooling system 400 of FIG. 8. Control begins at start block230 and proceeds to decision block 232. At decision block 232,controller 146, or other portion of the system, determines whether afault condition has been detected in a pumping unit. If no faultcondition has been detected, control proceeds back to decision block232. If a fault condition has been detected, control proceeds to block234. At block 234, controller 146 brings the standby pumping unit, 120′in this example, online so that standby pumping unit 120′ can providepressurized fluid flow. Control then proceeds to block 236 wherecontroller 146 places the standby pumping unit 120′ into the coolingloop of the fault condition pumping unit 120. This occurs by openingrespective inlet valves 212 and outlet valves 208. This enables pumpingunit 120′ to provide fluid flow to load 122. Control then proceeds toblock 238 where the fault condition pumping unit 120 is removed from thecircuit. Controller 146 removes the fault condition pumping unit 120 byclosing its corresponding inlet valve 220 and outlet valve 218 in orderto take the fault condition pumping unit out of its respective coolingloop.

Control proceeds to decision block 240. At decision block 240,controller 146, or other portions of the system, determine when thefault condition pumping unit is determined to be operating properly. Ifthe fault condition pumping unit is not operating properly, controlreturns to decision block 240. If the fault condition pumping unit isoperating properly, control proceeds to block 242, and controller 146brings the now properly operating pumping unit 120 back online so thatit can be reinserted into its respective cooling loop to provide fluidflow of cooling fluid to the loads 122. Once the fault condition pumpingunit is brought online, control proceeds to block 244. At block 244, thefault condition pumping unit is placed into its respective cooling loopby opening its respective inlet valve 220 and outlet valve 218. Controlthen proceeds to block 246. At block 226, controller 146 removes thestandby pumping unit 120′ from the cooling loop by closing respectivestandby inlet valve 212 and outlet valve 208. Control then proceeds toblock 248 which takes redundant pumping unit 120′ offline. Control thenproceeds to end block 250.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

What is claimed is:
 1. A cooling system comprising: a primary coolingmodule, the primary cooling module supplying refrigerant to a circuitincluding a thermal load; a secondary cooling module, the secondarycooling module providing a supplemental flow of refrigerant to thecircuit upon detection of a deficiency of the primary cooling module;and at least one valve disposed between the primary cooling module andthe circuit to prevent refrigerant flow therebetween, wherein thesecondary cooling module is configured to transition from a standby modeof operation to an online mode of operation upon detection of a fault inthe primary cooling module.
 2. The cooling system of claim 1 wherein theprimary cooling module further comprises: a first pump for supplyingrefrigerant, the first pump supplying refrigerant to the circuit at afirst temperature; and a first condenser for receiving refrigerant fromthe circuit, the refrigerant received by the first condenser being at ahigher temperature than the first temperature.
 3. The cooling system ofclaim 2 wherein the secondary cooling module further comprises: a secondpump for supplying refrigerant, the second pump supplying refrigerant tothe circuit at the first temperature; and a second condenser forreceiving refrigerant from the circuit, the refrigerant received by thesecond condenser having a higher temperature than the first temperature.4. The cooling system of claim 3, the at least one valve furthercomprising: an inlet valve for controlling fluid flow between an inletof the circuit and one of the primary cooling module and the secondarycooling module; and an outlet valve for controlling fluid flow betweenan outlet of the circuit and one of the primary cooling module and thesecondary cooling module.
 5. The cooling system of claim 1, the at leastone valve further comprising: an inlet valve for controlling fluid flowbetween an inlet of the circuit and one of the primary cooling moduleand the secondary cooling module; and an outlet valve for controllingfluid flow between an outlet of the circuit and one of the primarycooling module and the secondary cooling module.
 6. A cooling systemcomprising: a plurality of primary cooling modules, the primary coolingmodules circulating refrigerant through a respective one of a pluralityof thermal loads; a secondary cooling module, the secondary coolingmodule selectively providing a supplemental flow of refrigerant througha load associated with a primary cooling module for which a fault hasbeen detected; and at least one valve disposed between each of theplurality of primary cooling modules and the load to prevent refrigerantflow therebetween, wherein the secondary cooling module is configured totransition from a standby mode of operation to an online mode ofoperation upon detection of the fault in the primary cooling module forwhich a fault has been detected.
 7. The cooling system of claim 6wherein each primary cooling module further comprises: a plurality offirst pumps for circulating refrigerant, the plurality of first pumpssupplying refrigerant at a first temperature to the respective loadsassociated with the respective primary cooling modules; and a pluralityof first condensers for receiving refrigerant from the respective loadsassociated with the respective primary cooling modules, the refrigerantreceived by the respective condensers being at a higher temperature thanthe first temperature.
 8. The cooling system of claim 7 wherein thesecondary cooling module further comprises: a second pump for supplyingrefrigerant, the second pump supplying refrigerant at the firsttemperature to the load associated with the primary cooling module forwhich the fault has been detected; and a second condenser for receivingrefrigerant from the load associated with the primary cooling module forwhich the fault has been detected, the refrigerant received by thesecond condenser having a temperature higher than the first temperature.9. The cooling system of claim 8, the at least one valve furthercomprising: a plurality of inlet valves associated with a respectiveprimary cooling module for controlling fluid flow between an inlet ofthe respective load and a respective primary cooling module and thesecondary cooling module; and an plurality of outlet valves associatedwith a respective primary cooling module for controlling fluid flowbetween an outlet of the respective load and a respective primarycooling module and the secondary cooling module.
 10. A method forproviding redundant cooling in a cooling system comprising: providing aprimary cooling module having a circuit, the primary cooling moduleproviding cooling fluid to a thermal load; providing a secondary coolingmodule; arranging at least one valve between the primary cooling moduleand the load to prevent refrigerant flow therebetween; initiatingoperation of the secondary cooling module upon detection of a fault inthe primary cooling module; inserting the secondary cooling module intothe circuit, the secondary cooling module providing cooling fluid to thethermal load; deactivating the primary cooling module; and transitioningthe secondary cooling module from a standby mode of operation to anonline mode of operation upon detection of the fault in the primarycooling module.
 11. The method of claim 10 further comprising removingthe primary cooling module from the circuit.
 12. The method of claim 10further comprising returning the cooling system to normal operationcomprising: transitioning the primary cooling module from a standby modeof operation to an online mode of operation when the fault is no longerdetected; inserting the primary cooling module into the circuit forproviding cooling fluid to the thermal load; and transitioning thesecondary cooling module to the standby mode of operation.
 13. Themethod of claim 12 further comprising removing the secondary coolingmodule from the circuit.